Integral two layer preform, process and apparatus for the production thereof, process for producing a blow-moulded bag-in-container, and bag-in-container thus produced

ABSTRACT

The invention is an integral two-layer preform for the production of integrally blow-moulded bag-in-containers. The preform has an inner layer and an outer layer, wherein the preform forms a two layer container upon blow-moulding, and wherein the thus obtained inner layer of the container releases from the thus obtained outer layer upon introduction of a gas at a point of interface of the two layers. The melting temperature of the inner layer is greater than or equal to the melting temperature of the outer layer.

FIELD OF THE INVENTION

The present invention relates in general to new developments indispensing bag-in-containers and, in particular, to Integral two layerpreforms particularly advantageous for the production of integrallyblow-moulded bag-in-containers. It also relates to a method forproducing said preforms and bag-in-containers.

BACKGROUND OF THE INVENTION

Bag-in-containers, also referred to as bag-in-bottles or bag-in-boxesdepending on the geometry of the outer vessel, all terms consideredherein as being comprised within the meaning of the termbag-in-container, are a family of liquid dispensing packaging consistingof an outer container comprising an opening to the atmosphere the mouthand which contains a collapsible inner bag joined to said container andopening to the atmosphere at the region of said mouth. The system mustcomprise at least one vent fluidly connecting the atmosphere to theregion between the inner bag and the outer container in order to controlthe pressure in said region to squeeze the inner bag and thus dispensethe liquid contained therein.

Traditionally, bag-in-containers were and still are produced byindependently producing an inner bag provided with a specific neckclosure assembly and a structural container (usually in the form of abottle). The bag is inserted into the fully formed bottle opening andfixed thereto by means of the neck closure assembly, which comprises oneopening to the interior of the bag and vents fluidly connecting thespace between bag and bottle to the atmosphere; examples of suchconstructions can be found inter alia in U.S. Pat. No. 3,484,011, U.S.Pat. No. 3,450,254, U.S. Pat. No. 4,330,066, and U.S. Pat. No.4,892,230. These types of bag-in-containers have the advantage of beingreusable, but they are very expensive and labour-intensive to produce.

More recent developments focused on the production of “integrallyblow-moulded bag-in-containers” thus avoiding the labour-intensive stepof assembling the bag into the container, by blow-moulding a polymericmultilayer preform into a container comprising an inner layer and anouter layer, such that the adhesion between the inner and the outerlayers of the thus produced container is sufficiently weak to readilydelaminate upon introduction of a gas at the interface. The “innerlayer” and “outer layer” may each consist of a single layer or aplurality of layers, but can in any case readily be identified, at leastupon delamination. Said technology involves many challenges and manyalternative solutions were proposed.

The multilayer preform may be extruded or injection moulded (cf. U.S.Pat. No. 6,238,201, JPA10128833, JPA11010719, JPA9208688, U.S. Pat. No.6,649,121). When the former method is advantageous in terms ofproductivity, the latter is preferable when wall thickness accuracy isrequired, typically in containers for dispensing beverage.

Preforms for the production of integrally blow-moulded bag-in-containersclearly differ from preforms for the production of blow-mouldedco-layered containers, wherein the various layers of the container arenot meant to delaminate, in the thickness of the layers. Abag-in-container is comprised of an outer structural envelope containinga flexible, collapsible bag. It follows that the outer layer of thecontainer is substantially thicker than the inner bag. This samerelationship can of course be found in the preform as well, which arecharacterized by an inner layer being substantially thinner than theouter layer. Moreover, in some cases, the preform already comprisedvents which are never present in preforms for the production ofco-layered containers (cf. EPA1356915).

The formation of the vents fluidly connecting the space or interfacebetween bag and bottle to the atmosphere remains a critical step inintegrally blow-moulded bag-in-containers and several solutions wereproposed in e.g., U.S. Pat. No. 5,301,838, U.S. Pat. No. 5,407,629,JPA5213373, JPA8001761, EPA1356915, U.S. Pat. No. 6,649,121,JPA10180853.

One redundant problem with integrally blow-moulded bag-in-containers isthe choice of materials for the inner and outer layers which must beselected according to strict criteria of compatibility in terms ofprocessing on the one hand and, on the other hand, of incompatibility interms of adhesion. These criteria are sometimes difficult to fulfil incombination.

The preform usually consists of an assembly of two separate preforms andproduced independently from one another and thereafter assembled suchthat the inner preform fits into the outer preform as illustrated inJPA10180853. This solution allows for greater freedom in the design ofthe neck and vents, as well as in the choice of materials for the innerand outer layers: the compatibility in terms of processing between thematerials of the inner and outer layers concern the blow-mouldingoperation only. It is, however, expensive as it requires two separateproduction lines and an assembly line.

Replacing a preform assembly as discussed above by an integral preformobtained by injection moulding one layer on top of the other offers ofcourse a number of potential advantages in terms of production costs.Other problems, however, arise and need be addressed. In particular, thechoice of materials for the inner and outer layers is more complex sincethey must be compatible in terms of process in both the injectionmoulding and the blow-moulding operations. U.S. Pat. No. 5,301,838discloses a complex injection moulded, five layer, integral preformcomprising three PET layers interleaved by two thin layers of a materialselected from the group of EVOH, PP, PE, PA6. This solution, however, isquite complex and requires that the materials of the thin layers have“little if any primary affinity for (i.e;, tendency to chemically bondor adhere to) the adjacent [PET] layers,” which unduly restricts thechoice of materials to be used.

EPA1356915 and U.S. Pat. No. 6,649,121 proposes that the materials forthe inner and outer layers of the preform should be selected such thatthe melting temperature of the outer layer is higher than the one of theinner layer, T_(m,outer)>T_(m,inner), lest a strong bond would formbetween layers when the inner layer is injection moulded over the outerlayer, which had been injected into the mould cavity first. Examples ofmaterials for the outer layer given by the authors include PET and EVOH,whilst polyethylene is given as an example for the inner layer.

It follows from the foregoing that there remains room in the art forsolutions for the production of integral preforms made of materialscompatible in terms of processing, both for the injection moulding andblow-moulding operations, and yielding bag-in-containers with gooddelamination properties.

SUMMARY OF THE INVENTION

The present invention is defined in the appended independent claims.Preferred embodiments are defined in the dependent claims. In particularthe present invention relates to an integral two-layer preform and abag-in-container produced by blow-moulding the preform, the preformcomprising an inner layer and an outer layer, wherein the preform formsa two layer container upon blow-moulding, and wherein the thus obtainedinner layer of said container releases from the thus obtained outerlayer upon introduction of a gas at a point of interface of the twolayers. The melting temperature of the inner layer is greater or equalto the melting temperature of the outer layer.

Preferably, the preform comprises at least one interface vent runningparallel to the interface between the inner and outer layer, and openingto the atmosphere at a location adjacent to, and oriented coaxially withthe preform's mouth.

It also concerns a process for the production of a preform as definedabove comprising the following sequential steps:

-   -   injection moulding the inner layer onto a core;    -   injection moulding the outer layer onto the inner layer;    -   extracting the thus formed preform from the core;

wherein the melting temperature of the inner layer is greater or

equal to the melting temperature of the outer layer.

The foregoing process is advantageously carried out for the productionof said preform comprising at least one interface vent, by using a toolof the core-shell type, characterized in that it comprises a core mouldprovided at the base thereof with at least one pin, preferably wedgeshaped, suitable for forming a vent at the interface between the firstand second layers of said preform.

The invention further addresses an apparatus for producing a preform asdefined above of comprising:

-   -   support means provided with at least two similar cores (male);    -   at least first and second shell moulds (female) each connected        to an extruder, such that the first shell mould is dimensioned        for producing in combination with a core the inner layer and the        second shell mould for producing the outer layer on top of the        inner one;    -   optionally at least one extraction station,    -   means for moving the support means so that each core can be        positioned sequentially opposite the first shell mould, the        second shell mould, and optionally the extraction station.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic cross-sectional representation of a preform andthe bag-in-container obtained after blow-moulding thereof.

FIG. 2 is a cutaway perspective view of the mouth and neck region of apreform or bag-in-container according to a preferred embodiment of thepresent invention.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to appended FIGS. 1A and 1B, there is illustrated anintegrally blow-moulded bag-in-container (2) and a preform (1)&(1′) forits manufacturing. The preform (1) comprises an inner layer (11) and anouter layer (12) joined at least at the level of the neck region (6) byan interface (shown on the right hand side). The region between innerand outer layers(11) and (12) may either consist of an interface (14)wherein the two layers are substantially contacting each other, orcomprise a gap (14′) in fluid communication with at least one vent (3)opening to the atmosphere in (4).

Many vent geometries have been disclosed and it is not critical whichgeometry is selected. It is preferred, however, that the vent be locatedadjacent to, and oriented coaxially with said preform's mouth (5) asillustrated in FIG. 1. More preferably, the vents have the shape of awedge with the broad side at the level of the opening (4) thereof andgetting thinner as it penetrates deeper into the vessel, until the twolayers meet to form an interface (14) at least at the level of the neckregion as illustrated in FIG. 2. This geometry allows for a moreefficient and reproducible delamination of the inner bag upon use of thebag-in-container. The container may comprise one or several vents evenlydistributed around the lip of the bag-in-container's mouth. Severalvents are advantageous as they permit the interface of the inner andouter layers(21) and (22) of the bag-in-container (2) to release moreevenly upon blowing pressurized gas through said vents. Preferably, thepreform comprises two vents opening at the vessel's mouth lip atdiametrically opposed positions. More preferably, three, and mostpreferably, at least four vents open at regular intervals of the mouthlip.

The preform of the present invention consists of an integral preformobtained by injection moulding one layer on top of the other. Thissolution offers a number of advantages over preform assemblies, like forinstance, that it requires no assembly step and one production stationonly is sufficient for the integral preform fabrication when at leasttwo are required for a preform assembly.

Preferred materials for the layers of the preform and bag-in-containerof the present invention are polyesters like PET, PEN, PTT, PTN;polyamides like PA6, PA66, PA11, PA12; polyolefins like PE, PP; EVOH;biodegradable polymers like polyglycol acetate (PGAc), Polylactic acid(PLA); and copolymers and blends thereof. The requirement according tothe present invention for the materials of the inner and outer layers isthat the melting temperature of the outer layer is lower than, or equalto the one of the inner layer, T_(m,outer)<T_(m,inner). This conditionis exactly the opposite to the one taught in EPA1356915 and U.S. Pat.No. 6,649,121. This departure from the teaching of said prior art isrendered possible by the discovery by the present inventors that theintegral preform can advantageously be produced with the followingsequential steps:

-   -   injection moulding the inner layer first onto a core;    -   followed by injection moulding the outer layer onto the inner        layer; and    -   extracting the thus formed preform from the core;

This approach is more advantageous than the one proposed in EPA1356915and U.S. Pat. No. 6,649,121 for the following reasons. As discussed inthe review of the background art, a bag-in-container must comprise atleast one interface vent fluidly connecting the interface between innerand outer layers to the atmosphere. In the field of beverage dispensingcontainers, the assembled (i.e., not integrally blow-moulded)bag-in-containers used to date, traditionally and for practical reasons,are provided with vents located adjacent to, and oriented coaxially withthe bag-in-container's mouth. So as to progressively replace thetraditional, assembled bag-in-containers by integrally blow-mouldedones, and so as to allow the consumer to keep the same appliance thebag-in-container is to be mounted into, the same vents location ispreferably maintained. The present process allows to provide integralpreforms with vents fluidly connecting the interface between inner andouter layers to the atmosphere, provided an appropriate tool is used.

The tool is of the core-shell type and comprises a core mould providedat the base thereof with at least one pin suitable for forming a vent atthe interface between the first and second layers of the preform. Thecore may comprise a single pin, but it preferably comprises more thanone pin in order to have several vents opening around the lip of thecontainer's mouth. The pins preferably have the shape of a wedge as, onthe one hand, a wedge shaped vent has the advantages discussed aboveand, on the other hand, it allows for easier extraction of the thusproduced integral preform from the mould core. The dimensions of thepins depend on the size of the bag-in-container and, in particular, ofthe mouth and lip thereof. For a typical home beverage dispenser of acapacity of about 56 liters, the pins have a height of about 5 to 75 mm,preferably 5 to 50 mm, most preferably 10 to 20 mm and their base,forming the vents openings, preferably are in the shape of an arcsection of length comprised between 3 and 15 mm, preferably 5 and 10 mmand of width comprised between 0.5 and 5 mm, preferably 0.5 and 2 mm.

Preferably, the integral preform of the present invention comprisesmechanical interlocking means (8) for fixing the inner layer to theouter layer. This allows an easier and safer handling of the preform andfacilitates the extraction of the preform from the injection mouldingcore.

The preform of the present invention can be produced semicontinuouslywith an apparatus comprising:

-   -   support means provided with at least two similar cores (male),        preferably of the type described above;    -   at least first and second shell moulds (female) each connected        to an extruder, such that the first shell mould is dimensioned        for producing in combination with a core the inner layer and the        second shell mould for producing the outer layer on top of the        inner one;    -   optionally at least one extraction station,    -   means for moving the support means so that each core can be        positioned sequentially opposite the first shell mould, the        second shell mould, and optionally the extraction station.

The apparatus of the present invention may include a separate extractionstation, for example to allow further cooling of the part prior toextraction or, if the preform is extracted upon opening the mould afterthe injection of the second layer, it may well do without one. The meansfor moving the support means from one shell mould to the other and,optionally, to the extraction station may be linear, using a “shuttle,”or rotational, using a “carrousel.”

The two layers (11) and (12) of the preform according to the presentinvention are connected by an interface (14) throughout substantiallythe whole inner surface of the outer layer. Although the inner and outerlayers of the preform may adhere at said interface (14), the inner andouter layers (21) and (22) of the bag-in-container (2) produced byblow-moulding the preform (1) do delaminate upon injection of apressurized gas at a point of the interface. It is generally believedthat better results are obtained when at least one of the inner andouter layers comprises a semi-crystalline polymer.

It has surprisingly been observed that excellent delamination resultsbetween the inner and outer layers of bag-in-containers can be obtainedalso with integral preforms wherein both inner and outer layers consistof the same material. This discovery is in contradiction with theteaching of the prior art with respect to the choice of materials of theinner and outer layer which, as quoted from JPA2005047172, must consistof “mutually non-adhesive synthetic resins.” It has now been shown thatexcellent integrally blow-moulded bag-in-containers may be produced withthe inner and outer layers made of the same material. Hence, accordingto the present invention, the melting temperature of the inner layer canbe equal to the melting temperature of the outer layer.

The same polymer is considered in contact on either side of theinterface between the inner and outer layers in the following cases:

-   -   inner and outer layers consist of the same material (e.g.,        PET_(inner)PET_(outer), regardless of the specific grade of each        PET); or    -   the inner and outer layers consist of a blend or copolymer        having at least one polymer in common, provided said polymer in        common is at the interface, whilst the differing polymer is        substantially absent of said interface (e.g., (0.85 PET+0.15        PA6)_(inner)(0.8 PET+0.2 PE)_(outer).

The presence in a layer of low amounts of additives is not regarded asrendering the material different, so far as they do not alter theinterface substantially.

The bag-in-container (2) of the present invention can be obtained byproviding a preform as described above; bringing said preform toblow-moulding temperature; fixing the thus heated preform at the levelof the neck region with fixing means in the blow-moulding tool; andblow-moulding the thus heated preform to form a bag-in-container. Theinner and outer layers (21) and (22) of the thus obtainedbag-in-container are connected to one another by an interface (24) oversubstantially the whole of the inner surface of the outer layer. Saidinterface (24) is in fluid communication with the atmosphere through thevents(3), which maintained their original geometry through theblow-moulding process since the neck region of the preform where thevents are located is held firm by the fixing means and is not stretchedduring blowing.

It is essential that the interface (24) between inner and outer layers(21) and (22) releases upon blowing pressurized gas through the vents ina consistent and reproducible manner. The success of said operationdepends on a number of parameters, in particular, on the interfacialadhesive strength, the number, geometry, and distribution of the vents,and on the pressure of the gas injected. The interfacial strength is ofcourse a key issue and can be modulated by the choice of the materialfor the inner and outer layers, and by the process parameters duringblow-moulding; the pressure-time-temperature window used is of course ofprime importance and greatly depends on the material selected for theinner and outer layers.

Example:

A preform according to the present invention was produced by injecting amelt into a first mould cavity cooled to form the preform's inner layer.The core comprising the inner layer was moved to a second cavity cooledat the same temperature as the first one, and a melt was injected overthe inner layer present in the cavity and the preform was extracted. Itcomprised vents (3) and interlocking means (8) as illustrated in FIG. 2.

The preform produced as explained above was heated in an oven comprisingan array of IR-lamps and then fixed into a blow-moulding mould whichwalls were maintained at a desired temperature. Air was blown into thepreform under pressure. The thus produced bag-in-container was thenfilled with a liquid and connected to an appliance for dispensingbeverage comprising a source of compressed air in order to determine thedelamination pressure.

The delamination pressure was determined as follows. The interface ventsof the bag-in-container were connected to the source of compressed air.Air was injected through the vents at a constant pressure and theinterface between inner and outer layers was observed; the pressure wasincreased stepwise until delamination pressure was reached. Delaminationpressure is defined as the pressure at which the inner bag separatesfrom the outer layer over the whole of their interface and collapses.The surfaces of the thus separated layers were examined for traces ofbonding.

The delamination pressure of the bag-in-container described above was ofabout 05±0.1 bar overpressure and showed little trace of cohesivefracture between the inner and outer layers. This example demonstratesthat bag-in-containers of excellent quality can be produced withintegral preforms according to the present invention.

1. An integral two-layer preform for the production of integrallyblow-moulded bag-in-containers, said preform comprising: an inner layerand an outer layer, wherein said preform forms a two layer containerupon blow-moulding, and wherein the thus obtained inner layer of saidcontainer releases from the thus obtained outer layer upon introductionof a gas at a point of interface of said two layers; and the meltingtemperature of the inner layer is greater or equal to the meltingtemperature of the outer layer.
 2. The preform according to claim 1wherein at least one of the inner and outer layers comprises asemi-crystalline material.
 3. The preform according to claim 1, whereinthe inner and outer layer consist of different materials.
 4. The preformaccording to claim 1, wherein the inner and outer layer consist of thesame material.
 5. The preform according to claim 1, wherein the innerand outer layers consist of a material selected from PET, PEN, PTT, PA,PP, PE, HDPE, EVOH, PGAc, PLA, and copolymers or blends thereof.
 6. Thepreform according to claim 1, wherein the at least one point ofinterface is a vent in the shape of a wedge with the broad side at thelevel of the opening thereof and getting thinner as it penetrates deeperinto the vessel, until the inner and outer layers meet to form aninterface.
 7. The preform according to claim 6, wherein more than onevent are distributed around the lip of the preform's mouth.
 8. Thepreform according to claim 1, wherein the inner and outer layers of thepreform are connected by an interface throughout substantially the wholeinner surface of the outer layer.
 9. The preform according to claim 1wherein the inner and outer layers and are fixed to one another throughmechanical interlocking means located in the preform's neck region. 10.A process for the production of a preform having an inner layer and anouter layer, wherein said preform forms a two layer container uponblow-moulding, and wherein the thus obtained inner layer of saidcontainer releases from the thus obtained outer layer upon introductionof a gas at a point of interface of said two layers; and the meltingtemperature of the inner layer is greater or equal to the meltingtemperature of the outer layer, comprising the following sequentialsteps: injection moulding the inner layer onto a core; injectionmoulding the outer layer onto the inner layer, and extracting the thusformed preform from the core.
 11. The process according to claim 10,wherein said core is adapted for forming vents fluidly connecting theinterface between the inner and outer layers to the atmosphere.
 12. Atool of the core shell type suitable for the production of a preformhaving an inner layer and an outer layer, wherein said preform forms atwo layer container upon blow-moulding, and wherein the thus obtainedinner layer of said container releases from the thus obtained outerlayer upon introduction of a gas at a point of interface of said twolayers, and the melting temperature of the inner layer is greater orequal to the melting temperature of the outer layer, comprising a coremould provided at the base thereof with at least one pin suitable forforming a vent at the interface between the first and second layers ofsaid preform.
 13. The tool according to claim 12 comprising more thanone pin disposed around the perimeter of the core base.
 14. The toolaccording to claim 12, wherein the pins have the shape of a wedge. 15.An apparatus for producing a preform having an inner layer and an outerlayer, wherein said preform forms a two layer container uponblow-moulding, and wherein the thus obtained inner layer of saidcontainer releases from the thus obtained outer layer upon introductionof a gas at a point of interface of said two layers, and the meltingtemperature of the inner layer is greater or equal to the meltingtemperature of the outer layer, comprising: support means provided withat least two similar male cores; at least first and second shell femalemoulds each connected to an extruder, such that the first shell mould isdimensioned for producing the inner layer and the second shell mould forproducing the outer layer on top of the inner one; at least one optionalextraction station, and means for moving the support means so that eachcore can be positioned sequentially opposite the first shell mould, thesecond shell mould and, optionally, the extraction station.
 16. Theapparatus according to claim 15, wherein said means for moving thesupport impart a linear movement to the support means.
 17. The apparatusaccording to claim 15, wherein said means for moving the support imparta rotational movement to the support means.
 18. Integrally blow-mouldedbag-in-container produced by blow-moulding a preform comprising: aninner layer and an outer layer, wherein said preform forms a two layercontainer upon blow-moulding, and wherein the thus obtained inner layerof said container releases from the thus obtained outer layer uponintroduction of a gas at a point of interface of said two layers, andthe melting temperature of the inner layer is greater or equal to themelting temperature of the outer layer.